DECOMPOSITION OF N2O CATALYZED BY ZSM-5 TYPE ZEOLITES - THE ROLE OF IRON

The catalytic properties of ferrisilicates (analogs of ZSM-5 zeolites) in the reaction of N2O decomposition are studied. The catalytic behavior of ferrisilicates is shown to be determined by the presence of active sites (so-called alpha-centers) involving iron atoms. Decomposition of N2O on alpha-centers proceeds with formation of an active form of surface oxygen, which cannot be produced by O2 adsorption. The influence of iron on the concentration of alpha-centers and the rate of N2O decomposition is investigated in a wide range of iron contents (from 0.003 to 4.8 wt % Fe2O3). Comparison of the dependences obtained with those observed earlier for ZSM-5 type ferrialuminosilicates reveals the identity of the specific catalytic activities of active sites in both systems. Tle higher catalytic activity of the Fe-A-Si samples as compared with the Fe-Si systems could be accounted for by the influence of Al on the iron distribution in zeolite resulting in a higher concentration of active sites at the same iron content.